1. Field of the Invention
The present invention relates to a trigger device, and more particularly to a trigger device for a rivet gun that may be pulled and triggered in two steps. Pulling the trigger device to a first step activates the high-pressure airflow through the rivet gun to eject and discard a remaining core pin of a used rivet out of the rivet gun. Further pressing the trigger device to a second step stops the air flow and drives the rivet gun to pull a core pin of an unused rivet on the front end of the barrel of the rivet gun to finish a riveting operation.
2. Description of Related Art
Taiwan utility model patent applications No. M286081 and M272598 disclose conventional rivet guns for mounting rivets on at least two pieces so that the rivets securely hold the pieces together. A rivet has a cap and a core pin. The cap is T-shaped and has an enlarged end and a mounting end. The core pin is mounted longitudinally through, protrudes out of the cap and has two ends and a ball formed on one end and adjacent to the mounting end of the cap.
A conventional rivet gun comprises a barrel, a handle, a trigger, a pin collector and a valve member.
The barrel has a front end, a rear end and a vise assembly that may vise and pull a core pin of a rivet on the front end into the barrel. The handle is mounted perpendicularly on the barrel and has air passageways. The collector is a jar mounted on the rear end of the barrel to collect the ejected core pins. The pneumatic cylinder is mounted movably under the handle and capable of activating the vise assembly through pneumatic and hydraulic means. Furthermore, the pneumatic cylinder may be connected to a high-pressure air source such as an air bottle to implement the ejection of the core pin.
When the rivet gun is used to rivet two pieces such as boards or plates together, a rivet is mounted through the pieces. The enlarged end of the cap of the rivet abuts an inside piece and the front end of the barrel of the rivet gun abuts the enlarged end. The trigger is pulled to activate the vise assembly to pull a core pin on the cap into the barrel. The ball on the core pin longitudinally compresses and radially expands the mounting end of the cap into T-shape so that the expanded mounting end hooks on an outside piece to complete the riveting process. Then, the air output by the high-pressure air source flows through the barrel from the front end to the rear end and sucks the broken core pin vised by the vise assembly backward into the collector
However, when the external high-pressure air source is connected to the rivet gun, the high-pressure air source constantly outputs air into the rivet gun no matter whether the rivet gun is triggered or not. The high-pressure air source cannot selectively output air during the core pin ejected when the broken core pin is ejected and stop outputting during the vise assembly vising and pulling the core pin.
To overcome the shortcomings, the present invention provides a trigger device for a rivet gun to mitigate or obviate the aforementioned problems.